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Subject: Iris prints

Iris prints

From: Andrew Robb <arobb>
Date: Wednesday, January 6, 1999
In response to Karen Whitehair's query concerning exhibition of IRIS

1. Climate Control Levels

IRIS prints are well known to be very sensitive to water, so the
concern over climate control is a good one. Even small drops of
water will cause virtually immediate bleeding of the each of the
four dyes (cyan, magenta, yellow, and black). This appears to be
true for each of the many different dyes sets and papers. Coatings
have been applied to prints, but in my experience they do not really
solve this problem. (In addition Henry Wilhelm (see below) has
reported that coatings do little to improve light stability and in
fact can harm light stability.) This water sensitivity concerned me
in regard to humidifying these prints, as one might do in a
treatment of a cockled print.

I conducted a small experiment in which I placed IRIS prints (made
with the Lyson Fine Art Ink Set on Somserset Velvet paper, no
coating was applied) in a passive humidity chamber at 100%RH. Within
one hour there was a very significant color shift--neutral grays
became brownish in color, blues became greenish. Upon examination
under a microscope it became evident that the magenta dye dots had
become larger, probably due to taking on moisture and bleeding.
(This experiment was discussed at the AIC meeting in Arlington this
past year.) So clearly 100% RH levels should be avoided.

I will be conducting an experiment monitoring prints at different
RHs but have not yet begun it. My feeling is that at an elevated RH
(above 60%) IRIS prints are at risk. Therefore I would recommend for
non-climate controlled conditions that IRIS prints be framed in
sealed packages at an RH level between 30 and 45%.

2. Color longevity

The behavior of IRIS prints is determined by a number of factors:
the dye set used, the paper, and any after treatments (such as
coating) so it is important to know what these components are in a
particular IRIS print.  For example, Henry Wilhelm's IRIS light
fading data (which can be found at there is a wide range
of fading times for different dye sets, papers, and dye set/paper
combinations. That said, the light stability of dyes sets used to
make IRIS prints has improved substantially in the past few years.
Many dye set/paper combinations have similar or better fading
characteristics to contemporary chromogenic photographic papers.
Since you indicate that the prints have not yet been made ("most of
the prints will be about 17 x 22 inches in size") I would highly
recommend that you use Wilhelm's information in choosing a dye set
and paper combination to minimize light fading.

Another concern is the fading rate of any brighteners in the paper
itself. These are usually quite fugitive and over time will
extinguish due to light exposure. This causes the paper to appear
slightly yellow (its "natural" color).

3. Light levels

The issue of appropriate light levels is quite difficult to answer
for fugitive materials. On the one hand never exposing a print to
light will ensure it does not fade--at the cost of never seeing it.
On the other hand many prints are best seen at high light levels
(well above 15-20 fc)--at the cost eventually of depriving future
viewers of seeing an unfaded print.  Striking a balance between
these two extremes is something that involves a number of
institutional priorities and typically involves a compromise.

As you will see in looking at the light fading data, it may take a
considerable amount of light (and/or exposure time) to cause
significant changes, assuming you have a print made with a more
light stable dye set/paper combination. Generally the light level
recommendation for works of art on paper and photographs for a three
year tour is between 5 and 10 fc. I would try to keep with in this
range, especially due to the optical brightener issue raised above.
Admittedly this level of 5 - 10 fc does come at some expense to the
ideal or typical viewing conditions (say above 40 fc).

In summary, the behavior of IRIS prints is fairly complex and we
have only limited experience in regard to exhibiting them. Your
concern over treating them just as "glorified colored photocopies"
is a good one and I hope you will share your experiences with this
project as it proceeds.

Andrew Robb
Conservation of Photographs
922 N. Ivy St., #2
Arlington, VA

                  Conservation DistList Instance 12:57
                 Distributed: Tuesday, January 12, 1999
                       Message Id: cdl-12-57-001
Received on Wednesday, 6 January, 1999

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